Generally, a rolling bearing fitted with a seal ring (referred to hereunder as a seal ring fitted rolling bearing) is incorporated for use into a transmission for automobiles, and into a rotational support section of various types of machinery such as machine tools and electrical machines.
The transmission for automobiles of the present invention is provided between an engine and a driven wheel, and is used for changing the ratio between the rotational speed of the engine crank shaft and the rotational speed of the driven wheel. Here the transmission for automobiles, which is the object of the present invention, includes as well as manual transmissions, automatic transmissions of various constructions such as planetary gear systems, belt systems, and toroidal systems.
As a transmission for automobiles incorporating a seal ring fitted rolling bearing, there is disclosed in U.S. Pat. No. 4,309,916 a construction as shown in FIG. 5. This manual type transmission for automobiles shown in outline in FIG. 5 has lubricating oil (transmission oil) 30 contained inside a casing 29, and an input shaft 31 and an output shaft 32 provided concentrically and freely rotatable relative to each other inside the casing 29. Furthermore, a transmission shaft 33 is provided inside the casing 29, parallel with the input shaft 31 and the output shaft 32. The input shaft 31, output shaft 32 and transmission shaft 33 are each rotatably supported by ball bearings 1a with seal rings fitted therein (referred to hereunder as seal ring fitted ball bearings) for serving as rolling bearings.
Of these shafts, the input shaft 31 supports a driving side gear 34 serving as a power transmission member on the driving side. Moreover, the output shaft 32 supports by means of respective synchromesh units (not shown in the figure), driven side gears 35a, 35b, 35c and 35d serving as respective power transmission members on the driven side. At the time of operation, only one of the driven side gears 35a.about.35d rotates with the output shaft 32, the other driven side gears rotating relative to the output shaft 32. Furthermore, the transmission shaft 33, on the part facing the driving side gear 34 and the respective driven side gears 35a, 35b, 35c and 35d supports respective transmission gears 36a, 36b, 36c, 36d and 36e so as to be rotatable together with the transmission shaft 33. The respective transmission gears 36a, 36b, 36c, 36d and 36e are respectively engaged with the driving side gear 34 and the driven side gears 35a, 35b, 35c and 35d either directly or via an idler gear 37 used for reversing.
In the case of the invention disclosed in the abovementioned U.S. Pat. No. 4,309,916, the respective seal ring fitted ball bearings 1a incorporated into the transmission for automobiles such as described above are sealed type bearings filled with grease. That is to say, for these respective seal ring fitted ball bearings 1a, ones constructed as shown in FIG. 6 are used. This seal ring fitted ball bearing 1a comprises an outer ring 2 and an inner ring 3 disposed concentric with each other, a plurality of balls 4 serving as rolling members, a retainer 5, and a pair of seal rings 6a. An outer ring raceway 7 is provided on a central portion of the inner peripheral face of the outer ring 2, and an inner ring raceway 8 is provided on a central portion of the outer peripheral face of the inner ring 3. The balls 4 are provided between the outer ring raceway 7 and the inner ring raceway 8 and are retained by the retainer 5 so as to be freely rotatable. Due to the rotation of the plurality of balls 4, the outer ring 2 and the inner ring 3 are freely rotatable relative to each other.
Moreover, anchoring grooves 9 are formed on opposite end portions on the inner periphery of the outer ring 2 around the whole periphery. A pair of ring shaped seal rings 6a are provided the outer peripheral rim portions of which are anchored in the respective anchoring grooves 9. The seal rings 6a are formed in an overall ring shape from respective ring shaped metal rings 14 and resilient material 15 such as rubber like elastomer etc. The resilient material 15 has seal lips 13 the tip edge rims of which are provided on the inner peripheral rims of the resilient material 15 to go into respective recesses 12 formed around the whole periphery of outer peripheral face portions on the opposite ends of the inner ring 3, and come into sliding contact with a portion of these recesses 12.
In the case of the seal ring fitted ball bearing la constructed as described above, communication between a space 16 in which the balls 4 are disposed and the outer space outside of the space 16 is shut off. Hence foreign matter existing outside cannot enter into the space 16. Therefore, any increase in wear due to foreign matter at the contact portions between the outer ring raceway 7 and the inner ring raceway 8 and the rolling surfaces of the balls 4 is prevented, thus enabling an increase in the rolling fatigue life of the seal ring fitted ball bearing 1a.
With the rolling bearing incorporated into a transmission for automobiles as described above for rotatably supporting the shafts 31, 32 and 33, prior to the invention disclosed in U.S. Pat. No. 4,309,916, a so called open type ball bearing 38 having no seal rings as shown in FIG. 7, was used. Lubrication of this ball bearing 38 is effected by circulation of lubricating oil 30 (FIG. 5) contained inside the casing 29. However, hard foreign matter such as wear debris and shavings from the respective gears 34, 35a, 35b, 35c and 35d, 36a, 36b, 36c, 36d and 36e and 37 is mixed into the lubricating oil 30, and this foreign matter damages the outer ring raceway 7, the inner ring raceway 8, and the rolling surfaces of the balls 4 giving an increase in wear, so that the endurance of the ball bearing 38 is compromised. On the other hand, in the case of the above described seal ring fitted ball bearing la shown in FIG. 6, this foreign matter does not damage the outer ring raceway 7, the inner ring raceway 8 and the rolling surfaces of the balls 4, and hence the rolling fatigue life can be increased.
In the case of the seal ring fitted ball bearing 1a shown in FIG. 6, the seal rings 6a made up of the metal ring 14 and the resilient material 15 are used. Furthermore, lubricating grease is filled in the interior and hence cost is increased. Specifically, since the seal rings 6a are a tight seal having substantially no gap, it takes a substantially long time before the lubricant oil existing around the seal ring fitted ball bearing 1a enter the interior of the seal ring fitted ball bearing 1a for lubrication. Accordingly, the grease must be filled in it. In addition, when the lubricating oil 30 inside the casing 29 of the transmission for automobiles is exchanged, this grease remains unchanged. Consequently, lubrication of the seal ring fitted ball bearing 1a must be effected by the initially introduced grease, even though the lubricating oil 30 is exchanged several times. It is therefore necessary to use an expensive grease having a very long life, thus causing an increase in the overall cost of the seal ring fitted ball bearing 1a. Moreover, in the case of the seal ring fitted ball bearing 1a, since the seal lips 13 rub against the recesses 12, rotational torque is increased.
In view of the above situation, the present inventors have considered using a construction such as shown in FIG. 8 as a seal ring fitted ball bearing incorporated into the rotational support sections of various mechanical equipment such as transmissions for automobiles. In the case of the seal ring fitted ball bearing 1 shown in FIG. 8, a pair of ring shaped seal rings 6 are provided the outer peripheral rims of which are anchored in the anchoring grooves 9 formed in inner peripheral face portions on the opposite ends the outer ring 2 around the whole periphery thereof. That is to say, bent back portions 10 on the outer diameter side are formed on the outer peripheral rim portions of the thin metal plate seal rings 6, by bending back the outer peripheral rim portions of the thin metal plate to give an arcuate shape in cross-section, and the bent back portions 10 on the outer diameter side are tightly crimped into the anchoring grooves 9 so that the seal rings 6 are securely supported on the outer ring 2.
Moreover, bent portions 11 are formed on the inner peripheral rims of the seal rings 6, and the inner peripheral faces of these bent portions 11 face recesses 12 formed in the outer peripheral faces of opposite end portions of the inner rings 3 around the whole periphery thereof. These recesses 12 and bent portions 11 of the seal rings 6 constitute labyrinth seals, and prevent the ingress of external foreign matter into the space 16 between the inner peripheral face of the outer ring 2 and the outer peripheral face of the inner ring 3, in which the balls 4 are disposed.
In the case where a seal ring fitted ball bearing 1 constructed as described above is used for example for supporting the shafts 31, 32 and 33 constituting a transmission for automobiles such as shown in FIG. 5, the lubricating oil 30 contained inside the casing 29 is circulated inside the space 16 in which the balls 4 are disposed to thereby lubricate the contact portions of the outer ring raceway 7, the inner ring raceway 8 and the rolling faces of the balls.
The present inventors used the seal ring fitted ball bearing 1 as shown in FIG. 8 for supporting the various shafts 31, 32 and 33 constituting a transmission for automobiles such as shown in FIG. 5, and carried out experiments to determine the endurance. Instead of being better than for the case where the open type ball bearing 38 such as shown in FIG. 7 was used, the endurance was worse. While researching the reason for this, the present inventors identified the following cause. That is to say, in the case of the seal ring fitted ball bearing 1 shown in FIG. 8, the ingress of foreign matter to inside the space 16 can not be completely prevented by the labyrinth seal made up of the recesses 12 and the bent portions 11 of the seal rings 6. Furthermore, the foreign matter entering into the space 16, accumulated at the outer diameter side of the space 16 due to centrifugal force, and was blocked by the seal rings 6 from being discharged from inside the space 16, thus remaining thereinside. As a result, wear due to the foreign matter was increased at the contact portions of the outer ring raceway 7 and the inner ring raceway 8, and the rolling faces of the balls 4, thus shortening the rolling fatigue life of the seal ring fitted ball bearing 1.
On the other hand, in Japanese Patent Publication TOKUKAIEI No. 8-114235, and Japanese Utility Model Publication JITSUKAISHO Nos. 51-79252, 54-95655, 58-86924, 60-7326, and 60-89422, a seal ring fitted ball bearing is disclosed where the inner peripheral rims of seal rings are anchored in the outer peripheral surfaces on the end portions of an inner ring, and a labyrinth seal is provided between the outer peripheral rims of the seal rings and the inner peripheral surfaces of the end portions of an outer ring. However, with the seal ring fitted ball bearings disclosed in these publications, no consideration is given to lubrication using lubricating oil which is contaminated with hard foreign matter such as the wear debris and shavings from gears, such as with the transmission for automobiles.